Alex, Rather than 'local', I think I would prefer 'none'. Rather than saying what the client is intending to do, express that the client isn't asking for or doesn't need credentials/access from the catalog.
At least then, the catalog could skip the generation. -Dan On Mon, Oct 5, 2026 at 12:51 AM Alex Dutra <[email protected]> wrote: > Hi all, > > How about at least introducing a new enum constant "local" in the > X-Iceberg-Access-Delegation header? If the intent of that header was > to express capabilities, this new constant would convey the notion of > "I can work with my own credentials" more firmly than letting the > server second-guess. E.g.: "local,remote-signing,vended-credentials" > would mean the client can either work with vended credentials, remote > signing, or its own credentials. > > Thanks, > Alex > > On Tue, Sep 29, 2026 at 4:08 AM youngrae kim <[email protected]> > wrote: > > > > Thanks Dan and Alex. > > > > Dan, that background is helpful, and I take the point: with > storage-credentials and remote-signing-config > > the catalog can state what it provides, so the spec does not need to > mandate a failure when the requested > > mechanisms cannot be provided. Polaris will keep its current behavior as > an implementation choice, > > documented as such, and I will report that outcome on the Polaris list. > > > > The one thing I would still find useful is Alex's narrower point: a > sentence saying whether the > > header is a capability statement or a requirement, and what an absent > header means. > > That does not constrain what the catalog decides to provide; it only > tells servers and clients how to read the header. > > If there is appetite for that I am happy to draft it; otherwise I am > fine leaving the wording as is and > > letting the catalog-driven model evolve with the File type work. > > > > Thanks, > > Youngrae Kim > > > > 2026년 9월 29일 (화) 오전 6:28, Daniel Weeks <[email protected]>님이 작성: > >> > >> I'm not sure I agree with the model of a client bringing its own > credentials if the catalog is also responsible for controlling access > (can't really stop people from using that model, but as I said above, it > feels like an anti-pattern). > >> > >> The current wording in the spec was intentionally loose so that the > catalog can make decisions without being forced into specific > security/access decisions. I still don't think that updating the wording > would be flexible enough. > >> > >> I'm not sure what all catalogs do, but I can say that it's always safe > for the catalog to return credentials/remote config even if the client was > externally configured to use its own. The current reference implementation > bypasses that, I believe, but conceptually a client does not need to use > the mechanism provided by the catalog. This again feels like a bit of an > anti-pattern: if there's a reason to bring sidecar credentials, it implies > a gap in the delegation model that we should be looking into addressing. > >> > >> Dan > >> > >> On Mon, Sep 28, 2026 at 10:00 AM Alex Dutra <[email protected]> wrote: > >>> > >>> Hi all, > >>> > >>> > The delegation header intended to allow the client to communicate > its capabilities, but we've aligned more clearly on catalogs controlling > access as opposed to clients defining behavior. > >>> > >>> IMO, this header isn't ideal for communicating client capabilities. > >>> Notably, it fails to represent a key capability: that of using the > >>> client's own storage credentials to bypass access delegation entirely. > >>> Right now, the only way to imply this capability is by omitting the > >>> header altogether, which introduces ambiguity into the specification. > >>> Put simply, a client cannot explicitly communicate e.g.: "I can > >>> function either without access delegation or using vended credentials, > >>> but I do not support remote signing." > >>> > >>> Therefore, Apache Polaris today treats this header as an explicit > >>> requirement rather than just a capability statement. IOW, it treats > >>> the header presence as an indication that the client cannot function > >>> without access delegation, and that at least one specified mode must > >>> be satisfied. > >>> > >>> I would be interested to hear how other catalog implementations are > >>> approaching this. > >>> > >>> In any case, I still think that a minor spec clarification would be > >>> welcome, if for nothing else, at least to lift the ambiguity around > >>> what it means when the header is absent and clarify whether the header > >>> is a capability statement, or a requirement. > >>> > >>> Thanks, > >>> Alex > >>> > >>> > >>> On Mon, Sep 28, 2026 at 5:03 PM Daniel Weeks <[email protected]> > wrote: > >>> > > >>> > Youngrae, > >>> > > >>> > I think the issue with #2 above is that it's a bit of an > anti-pattern for the client to concurrently own access. Either the catalog > should be the authority on access or it shouldn't. Security around the > physical data shouldn't really be a negotiation between the client and the > server. If the catalog is delegating access to the data, it should be the > sole source of truth. > >>> > > >>> > It feels like we're trying to make this a negotiation between the > catalog and client, but the catalog should be responsible for access > delegation in a secure environment. > >>> > > >>> > The background on this header is important: The original access > control mechanism was remote signing only, which was not originally part of > the REST protocol (it was separate and S3 specific). We later introduced > vended credentials, but only through the config payload. Since then, a lot > has changed: we introduced the Storage Credentials and now the Remote > Signing Config, which means that we're in a much better position for the > catalog to clearly indicate which mechanism the client should use. The > mechanisms are more standardized, and clients should be able to report if > they cannot support what the catalog has provided. > >>> > > >>> > While there may be some residual value in the client signaling its > capabilities, I'm not convinced we need to change the wording in the spec > and we need to improve the other mechanisms as we evolve to support new > functionality like File type, which may mix different modes of access. > >>> > > >>> > The behavior you describe in Polaris is perfectly fine as an > implementation choice, but I don't think catalogs SHOULD fail if they > cannot provide any requested mechanism. The catalog can provide an > alternative (e.g. you requested signing, but I'm only providing > credentials), which the client can error on if it does not understand. > Alternatively, the catalog could reject all requested forms and return only > the metadata, effectively signaling that the client can only see the > metadata, but has no access to the physical data. > >>> > > >>> > -Dan > >>> > > >>> > > >>> > On Fri, Sep 25, 2026 at 8:18 PM youngrae kim <[email protected]> > wrote: > >>> >> > >>> >> Thanks Alex, Yufei and Dan. > >>> >> > >>> >> Dan, I think the catalog-controlled direction and Alex's wording > are compatible, and it may help to separate the two roles the header plays > today: > >>> >> > >>> >> 1. Which mechanism to use. > >>> >> That is already the catalog's decision in Polaris: the server picks > among the mechanisms > >>> >> it supports for that catalog and storage, and the header only tells > it which ones the client can consume. > >>> >> Nothing in the proposed sentence changes that. > >>> >> > >>> >> 2. Whether the client can access the data at all without > delegation. Today the header is the > >>> >> only signal a client has for "I have no storage credentials of my > own". > >>> >> If the catalog cannot provide any mechanism the client can consume, > the request cannot succeed in any > >>> >> useful sense, and the question is only where the failure surfaces: > at load time with a > >>> >> message naming the cause, or at the first data access with a > storage error. > >>> >> > >>> >> The proposed SHOULD covers exactly the empty-intersection case in > (2); a server that knows its > >>> >> clients carry their own credentials can still return the table, > which is why SHOULD rather than MUST seems right. > >>> >> > >>> >> If the longer-term direction is to rely less on the header, I would > be interested in how a > >>> >> catalog-driven model would express (2), for example the client > learning from /v1/config which > >>> >> mechanisms the catalog offers, so it can decide before loading a > table. That seems like a > >>> >> larger change than the clarification this thread started with, so I > would suggest landing the > >>> >> one-sentence clarification for the current header and taking the > catalog-driven model as a > >>> >> separate discussion, unless you see a conflict between the two. > >>> >> > >>> >> Thanks, > >>> >> Youngrae Kim > >>> >> > >>> >> 2026년 9월 26일 (토) 오전 8:52, Daniel Weeks <[email protected]>님이 작성: > >>> >>> > >>> >>> I'm not convinced that we're thinking about this the right way. > >>> >>> > >>> >>> The delegation header intended to allow the client to communicate > its capabilities, but we've aligned more clearly on catalogs controlling > access as opposed to clients defining behavior. > >>> >>> > >>> >>> If we leaned more into that direction, then access would be > determined by the catalog based on the availability of vented credentials > or the new remote signing configuration. > >>> >>> > >>> >>> There may be an opportunity here to rely less on the header and > give responsibility back on th e catalog to determine the access model. > >>> >>> > >>> >>> -Dan > >>> >>> > >>> >>> On Fri, Sep 25, 2026, 4:39 PM Yufei Gu <[email protected]> > wrote: > >>> >>>> > >>> >>>> I tend to agree with Alex and Youngrae. A fail-fast approach > provides a clear behavioral contract between the server and clients, while > the current spec introduces ambiguity. > >>> >>>> > >>> >>>> I am not sure if this ambiguity was intentional. Please chime in > if you can provide more context; otherwise, I suggest we update the spec to > eliminate it. > >>> >>>> > >>> >>>> Yufei > >>> >>>> > >>> >>>> > >>> >>>> On Thu, Sep 24, 2026 at 10:12 AM Alex Dutra <[email protected]> > wrote: > >>> >>>>> > >>> >>>>> Hi Youngrae, > >>> >>>>> > >>> >>>>> Thanks for starting this thread! > >>> >>>>> > >>> >>>>> I believe the phrase "via any or none of the requested > mechanisms" > >>> >>>>> requires clarification. > >>> >>>>> > >>> >>>>> If a client requests modes A and B, a server returning only mode > B is > >>> >>>>> perfectly acceptable. However, returning a 200 OK response with > >>> >>>>> neither mode A nor B represents an ambiguous outcome. > >>> >>>>> > >>> >>>>> The current wording likely assumes the client could theoretically > >>> >>>>> proceed using its own fallback storage credentials. In practice, > >>> >>>>> operators configure clients intentionally; requesting access > >>> >>>>> delegation "just in case" is unrealistic. A fail-fast error is a > >>> >>>>> better outcome, as opposed to letting the client proceed, only > to see > >>> >>>>> it fail later on. > >>> >>>>> > >>> >>>>> I propose updating the specification to mandate an error > response when > >>> >>>>> no requested mechanism is available, while also clarifying > whether > >>> >>>>> providing multiple delegation modes is supported: > >>> >>>>> > >>> >>>>> "The server MAY supply access via any or all of the requested > >>> >>>>> mechanisms. If none of the requested mechanisms is available, the > >>> >>>>> server SHOULD return an HTTP 400 (Bad Request) response." > >>> >>>>> > >>> >>>>> Thanks, > >>> >>>>> Alex > >>> >>>>> > >>> >>>>> On Wed, Sep 23, 2026 at 11:14 AM youngrae kim < > [email protected]> wrote: > >>> >>>>> > > >>> >>>>> > Hi all, > >>> >>>>> > The REST catalog spec describes X-Iceberg-Access-Delegation as > an "optional signal to the server that the client supports delegated access > via a comma-separated list of access mechanisms. The server may choose to > supply access via any or none of the requested mechanisms." [1] > >>> >>>>> > > >>> >>>>> > In Apache Polaris we recently discussed what a server should > do when the header is present but it can satisfy none of the requested > mechanisms, for example vended-credentials against an S3-compatible store > without STS, or remote-signing on a server that does not implement it [2]. > >>> >>>>> > > >>> >>>>> > Polaris fails such requests with HTTP 400 and a message naming > the reason, because in these cases the inability is a static property of > the catalog and a 200 without credentials would only move the failure to > the first data access. > >>> >>>>> > > >>> >>>>> > Two readings of "any or none" came up and the text does not > settle which is intended: > >>> >>>>> > (a) "none" means the server returns 200 with the table and > no delegated access, and the client detects this from the response: an > empty storage-credentials (and, we understand, an empty > remote-signing-config once that field lands in 1.12), falling back to the > config map for older servers [3]. > >>> >>>>> > > >>> >>>>> > (b) "none" also permits the server to reject the request > when it cannot provide any of the requested mechanisms. > >>> >>>>> > > >>> >>>>> > Questions for the community: > >>> >>>>> > 1. Is rejecting the request a permitted server choice under > the current text, or is (a) the only intended behavior? > >>> >>>>> > 2. If rejection is permitted, is there a preferred status > code and error type, so clients can distinguish "delegation unavailable" > from other 400s? > >>> >>>>> > 3. If (a) is the intended behavior, should the spec state > explicitly that the absence of credentials in both storage-credentials and > config (and of remote-signing-config) is the signal that no delegation was > applied? > >>> >>>>> > > >>> >>>>> > I'm happy to draft a clarification to the parameter > description once there is agreement. > >>> >>>>> > > >>> >>>>> > [1] > https://github.com/apache/iceberg/blob/778d103c0fa802be5e85e4cb2e4e4b4bcd8ac891/open-api/rest-catalog-open-api.yaml#L2151-L2161 > >>> >>>>> > [2] > https://lists.apache.org/thread/9oyv4v0vk3t8stv9832npl8t0yyp4j8r > >>> >>>>> > [3] > https://github.com/apache/iceberg/blob/778d103c0fa802be5e85e4cb2e4e4b4bcd8ac891/open-api/rest-catalog-open-api.yaml#L4246-L4249 > >>> >>>>> > > >>> >>>>> > Thanks, > >>> >>>>> > Youngrae Kim >
